Today, in the modern society, batteries are one of the key electric parts indispensable as power sources for various electric appliances. Among them, a demand for the secondary battery whose charge/discharge can be repeated is steadily increasing.
The main secondary battery which has been put into practice includes a lead acid battery, a Ni—Cd (nickel—cadmium) battery, a Ni—MH (nickel-metal hydride) battery, a silver-zinc oxide battery, a lithium ion battery, etc.
The lead acid battery, in which lead dioxide is used as a positive active material, lead is used as a negative active material and dilute sulfuric acid is used as an electrolyte, has an operating voltage of 2 V. The lead acid battery has a good balance in quality, reliability and cost, and therefore is widely used for a motor vehicle, an electric vehicle, a UPS (uninterrutible power supply), etc. Further, since a technique of compact sealing has been developed in recent years, usefulness of the lead acid battery has been increased.
The Ni—Cd battery, in which nickel oxyhydroxide is used as a positive active material, cadmium is used as a negative active material and potassium hydroxide aqueous solution is used as an electrolyte, has an operating voltage of about 1.2 V. The Ni—Cd battery has features of a small internal resistance, allowability of large current discharge, long cycle life, resistance to excessive charge/discharge, and wide range of using temperature, etc. has been widely used for various consumer appliances.
The Ni—MH battery, in which nickel oxyhydroxide is used as a positive active material, a hydrogen storage alloy is used as a negative active material and potassium hydroxide aqueous solution is used as an electrolyte, has an operating voltage of about 1.2 V. The Ni—MH battery having a feature of a high energy density has been mainly put into practice for various consumer appliances.
The silver oxide zinc battery, in which silver oxide is used as a positive active material, zinc is used as a negative active material, and potassium hydroxide aqueous solution is used as an electrolyte, has features of a high output and a high energy density, but a defect of high cost. Therefore, its larger scale type has been mainly used for space and deep-sea equipment, whereas its small scale type has been widely used for a watch or an electronic calculator.
The lithium ion battery, in which Li-metal composite oxide such as LiCoO2, LiNiO2, LiMn2O4, etc. is used as a positive active material, a carbonaceous material is used as a negative electrode and an organic solution is used as an electrolyte, has an operating voltage of 3 V level. The lithium ion battery, which has features of a high operating voltage, high energy density and no memory effect, has been explosively used for consumer appliances.
Regardless of the primary battery and secondary battery, the batteries described above have been provided in the form of a rectangle, cylinder, button, sheet, etc. and adopted various output terminals according to the electric appliance in which the battery is used.
FIG. 1 is an appearance view of a prior art rectangular battery which has been widely used for motor vehicles. As seen from FIG. 1, two cylindrical positive and negative terminals 1a and 1b are provided convexly from the upper surface of the battery.
FIGS. 2A and 2B are sectional views of other prior art cylindrical batteries. Specifically, FIG. 2A shows two pin-like output terminals 1a and 1b provided convexly from the upper surface. FIG. 2B shows a single pin-like output terminal 1a with one polarity provided convexly from the upper surface and a bottomed cylindrical metallic battery vessel 2a which is used as an output terminal with another polarity.
FIG. 3 is an appearance view of still another prior art flat rectangular battery in which a protrusive terminal 3 attached to the one surface is used as an output terminal with one polarity and a bottomed rectangular battery vessel 2b is used as an output with another polarity.
FIG. 4 is a partially cut-away view of a further prior art flat battery in which two plate-like terminals 1a and 1b are attached to the one edge of a flat sack-shape battery vessel 2c. 
Conventionally, connection between the battery and the appliance using the battery has been made in a manner of connection by two wires and providing the appliance with two contacts. Therefore, there have been problems of troublesome connecting operations and complicated design of the arrangement of the terminals on the instrument. There has been another problem that the demand of arranging positive and negative output terminals on the one end face of the battery cannot be realized because the diameter of the battery is small. This invention has been accomplished in order to solve these problems.